640847 has 2 divisors, whose sum is σ = 640848. Its totient is φ = 640846.

The previous prime is 640837. The next prime is 640853. The reversal of 640847 is 748046.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640847 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640847.

It is not a weakly prime, because it can be changed into another prime (640837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320423 + 320424.

It is an arithmetic number, because the mean of its divisors is an integer number (320424).

2⁶⁴⁰⁸⁴⁷ is an apocalyptic number.

640847 is a deficient number, since it is larger than the sum of its proper divisors (1).

640847 is an equidigital number, since it uses as much as digits as its factorization.

640847 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 640847 is about 800.5291999671. The cubic root of 640847 is about 86.2153876381.

The spelling of 640847 in words is "six hundred forty thousand, eight hundred forty-seven".